This invention relates to an auto-adjusting mechanism for a disc brake including a parking brake, more particularly, to an adjusting mechanism capable of preferably preventing a dragging of brake pads (residual friction of brake pads onto the disc rotor) caused by an over adjustment.
As an auto-adjusting mechanism for a type of disc brake including a parking brake, a proposition has been made, in which a cylinder body accommodating a piston for urging the brake pads onto the disc rotor is provided with an adjust bolt axially slidably attached and an adjust nut unidirectionally rotatably attached to the former, and the piston is, when the disc brake is used as a parking brake, bestowed a thrusting force by way of the bolt and the nut, whereby when the brake pads have been worn thin, the adjust nut is given a forward directional thrust, by the piston which is advanced by the braking fluid pressure in an normal braking operation, to rotatingly advance a distance corresponding to the worn amount of the brake pads. In a conventional adjusting mechanism of this type, the adjust nut is liable to advance too much, when the braking fluid pressure is particularly raised high due to an emergency braking or some other reasons, for compensating even the elastic deformation of other brake components such as a caliper, which being an over-adjustment. The over-adjustment often causes, as is well known, a dragging of the brake pads and sometimes leads to locking of the wheels.
As a cure of such disadvantage of over-adjustment, making the distance between the adjust nut and the piston larger than the amount of elastic deformation taking place in the caliper or others was thought of. It brings about, however, an inevitable resultant increase of stroke of the braking mechanism, such as the parking lever and the braking pedal.